A plan to start repatriating Rohingya Muslims back to Myanmar is premature and the refugees are "terrified" about leaving Bangladesh where they sought refuge, dozens of aid agencies working in the region said Friday.

Rohingya men fill bags with bricks at the Kutupalong camp near Cox's Bazar in Bangladesh on July 18, 2018.ST PHOTO: KUA CHEE SIONG

More than 720,000 Rohingya Muslims fled Myanmar's northern Rakhine state to Bangladesh after a heavyhanded army crackdown in August that survivors say involved mass rape and extrajudicial killings.

UN investigators say that the country's military leaders should be investigated for genocide but Myanmar has rebuffed the calls, arguing it was only defending itself against Rohingya militants who attacked police posts.

Both Bangladesh and Myanmar signed a repatriation agreement to allow Rohingya to return but many fear going back without guarantees of citizenship, freedom of movement and safety.

However the governments said in recent weeks that they were pushing ahead with the first large-scale repatriation in mid-November, prompting an outcry from advocates who say conditions on the ground in Rakhine are not adequate.

"They fled to Bangladesh to seek safety and they are very grateful to the Government of Bangladesh for giving them a safe haven," the group of 42 aid agencies and civil society said in a statement that referred to the push as "dangerous."

"They are terrified about what will happen to them if they are returned to Myanmar now, and distressed by the lack of information they have received."

Oxfam, World Vision and Save the Children were among the groups working in Myanmar and Bangladesh that signed the statement.

They said refugees fear living in enclosed settlements like more than 120,000 Rohingya in central Rakhine state, who have been confined to camps for six years since intercommunal violence erupted in the region in 2012.

Northern Rakhine state has been largely sealed off since the crackdown except for highly organised government trips for media and senior visiting diplomats.

The UN has been granted access to the area to help assess conditions on the ground but the approvals have been slow and the amount of territory limited.

Authorities in Bangladesh worry that Rohingya may once again risk travelling to other parts of Southeast Asia by boat, a route previously popular as a way of seeking economic opportunities outside the grim camps.

This week Bangladesh's coast guard rescued 33 Rohingya and detained six alleged human traffickers from a fishing trawler headed for Malaysia in the Bay of Bengal.